A gas-insulated switchgear, configured in such a way that a high-voltage electric conductor, a switching device, an earthing device, and the like are connected with one another and contained in a metal container in which an insulating gas, such as an SF6 gas, having high-insulation performance is enclosed, has an advantage in that the insulation performance thereof is superior to that of an air-insulated switchgear, whereby the area required for installation is reduced; therefore, in recent years, the gas-insulated switchgear has widely been adopted in an electric power station, a substation, and the like.
In order to further downsize such a gas-insulated switchgear, various proposals have been implemented (refer to Patent Document 1); an example of gas-insulated switchgears disclosed in Patent Document 1 will be explained with reference to FIG. 7. FIG. 7 in which 7(a) is an elevation view and 7(b) is a plan view illustrates a gas-insulated switchgear applied to locations where double bus bars 2a to 2c and 3a to 3c that are horizontally arranged spaced an inter-phase distance L2 apart from one another are connected with transmission-line circuits 12a to 12c extending in a direction perpendicular to the double main bus bars, by way of circuit breakers 1a to 1c, disconnecting switches 6a to 6c, 7a to 7c, and 9a to 9c, and the like.
In FIG. 7(a), single-phase gas-insulated circuit breakers 1a to 1c for three phases are provided in parallel with one another in a direction perpendicular to the plane of the paper; only one single-phase gas insulated circuit breaker is illustrated in FIG. 7(a). A T-shaped connecting bus bars 5a is provided, by way of an instrument transformer 4a, at a bus-bar terminal 10 that is one of the lead exit portions of the single-phase gas-insulated circuit breaker 1a for one of the three phases; a T-shaped connecting bus bar 5b is provided, by way of an instrument transformer 4b, at a corresponding bus-bar terminal that is one of the lead exit portions of the single-phase gas-insulated circuit breaker 1b for one of the three phases; a T-shaped connecting bus bar 5c is provided, by way of an instrument transformer 4c, at a corresponding bus-bar terminal that is one of the lead exit portions of the single-phase gas-insulated circuit breaker 1c for one of the three phases; the first bus bar 2a is connected with the one end of the connecting bus bar 5a, by way of the first bus-bar disconnecting switch 6a; the first bus bar 2b is connected with the one end of the connecting bus bar 5b, by way of the first bus-bar disconnecting switch 6b; the first bus bar 2c is connected with the one end of the connecting bus bar 5c, by way of the first bus-bar disconnecting switch 6c; additionally, the second bus bar 3a is connected with the other end of the T-shaped connecting bus bar 5a, by way of the second bus-bar disconnecting switch 7a; the second bus bar 3b is connected with the other end of the T-shaped connecting bus bar 5b, by way of the second bus-bar disconnecting switch 7b; the second bus bar 3c is connected with the other end of the T-shaped connecting bus bar 5c, by way of the second bus-bar disconnecting switch 7c. 
In contrast, a transmission-line disconnecting switch 9a is provided, by way of an instrument transformer 8a, at a transmission-line terminal 11 that is the other one of the lead exit portions of the single-phase gas-insulated circuit breaker 1a; a transmission-line disconnecting switch 9b is provided, by way of an instrument transformer 8b, at a corresponding transmission-line terminal that is the other one of the lead exit portions of the single-phase gas-insulated circuit breaker 1b; a transmission-line disconnecting switch 9c is provided, by way of an instrument transformer 8c, at a corresponding transmission-line terminal that is the other one of the lead exit portions of the single-phase gas-insulated circuit breaker 1c; transmission-line circuits 12a to 12c are connected with the transmission-line disconnecting switches 9a to 9c, respectively. In addition, reference numeral 12 denotes an earthing device for executing earthing through the metal container.
However, in the gas-insulated switchgear configured as described above, the first bus bars 2a to 2c and the second bus bars 3a to 3c for three phases respectively are arranged in parallel with one another and spaced a predetermined inter-phase distance L2 apart from one another so that the single-phase bus bars do not interfere with one another. However, because the circuit breakers 1a to 1c for three phases are arranged overlapped as illustrated in FIG. 7(b), the respective lengths of the connecting bus bars 5a to 5c should be adjusted so as to make connection between the bus bars, for each phase, which are arranged spaced the inter-phase distance apart from each other; therefore, the T-shaped connecting bus bars 5a to 5c having different sizes in accordance with the respective circuit breakers corresponding to the three phases should be prepared, thereby preventing downsizing and standardization.
Therefore, according to Patent Document 1, by arranging the circuit breakers for the respective phases in parallel with one another and spaced the inter-phase distance between the bus bars apart from one another, thereby utilizing T-shaped connecting bus bars, having the same shape, for the respective three phases, the downsizing of the whole configuration and the standardization of constituent components are achieved.
However, even with the foregoing method, it has been a problem that, because the circuit breakers 1a to 1c are arranged spaced the inter-phase distance between the bus bars apart from one another and the first bus bars 2a to 2c and the second bus bars 3a to 3c are arranged in parallel with one another and in a horizontal manner with respect to a mounting plane F, the bus bars have been forced to arrange in such a way as to avoid the space corresponding to both the lead exit portions of the circuit breaker, whereby the overall mounting area is still large.
[Patent Document 1]
Japanese Laid-Open Patent Publication No. 1992-304105